Characterization of Low-Pressure Cold-Sprayed Aluminum Coatings
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JTTEE5 17:728–735 DOI: 10.1007/s11666-008-9254-5 1059-9630/$19.00 Ó ASM International
Characterization of Low-Pressure Cold-Sprayed Aluminum Coatings K. Ogawa, K. Ito, K. Ichimura, Y. Ichikawa, S. Ohno, and N. Onda (Submitted May 14, 2008; in revised form September 22, 2008) Aluminum alloys are widely used as materials for engineering components of automobiles and airplanes because of their light weight and high corrosion resistance. However, cracks may develop sometimes in aluminum components, which have to be repaired by welding. It is difficult to weld aluminum components due to its high specific thermal conductivity and high coefficient of thermal expansion. The lowpressure cold-spray technique can be used instead of welding for repairing cracks. However, the effects of surface conditions on particle deposition and the mechanical properties of cold-sprayed coatings have not been investigated thus far. In this study, the effect of surface conditions focusing on active newly formed surface on aluminum particle deposition is studied and the mechanical properties of low-pressure cold-sprayed aluminum coatings are investigated by four-point bending tests. It is found that for efficient particle deposition it was necessary to obtain active newly formed surface of the substrate and particle surfaces by several impingements because the existence of inactive native oxide films has an adverse effect on the deposition. Furthermore, the strength of a cold-sprayed specimen is found to be higher than that of a cold-rolled specimen under compressive loading.
Keywords
low-pressure cold spray, aluminum, bonding strength, characterization, deposition mechanism, four-point bending tests, newly-formed surface
1. Introduction Surfaces are widely coated to obtain the required surface conditions and properties. In the past, many coatings used have been applied using the thermal spray processes. In a conventional thermal spray process, the coating material is heated to the molten or semimolten state and impinged onto a substrate surface. Because of heating, thermal spray coatings show various unfavorable phenomena, e.g., oxidation, phase transformation, etc. A new coating technique, the cold-gas dynamic-spray process,
This article is an invited paper selected from presentations at the 2008 International Thermal Spray Conference and has been expanded from the original presentation. It is simultaneously published in Thermal Spray Crossing Borders, Proceedings of the 2008 International Thermal Spray Conference, Maastricht, The Netherlands, June 2-4, 2008, Basil R. Marple, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Ghislain Montavon, Ed., ASM International, Materials Park, OH, 2008. K. Ogawa, K. Ito, K. Ichimura, and Y. Ichikawa, Fracture and Reliability Research Institute, Tohoku University, Aoba 6-6-01, Aramaki, Aoba-ku, Sendai 980-8579, Japan; and S. Ohno and N. Onda, Tohoku Electric Power Co., Inc., 1-7-1, Honcho, Aoba-ku, Sendai 980-8550, Japan. Contact e-mail: kogawa@rift. mech.tohoku.ac.jp.
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